The invention relates to optical devices, and in particular to optical devices with reduced electrical consumption.
Automatic displacement driving devices applied in lens modules may employ drivers providing rotational power with a rotational axis thereof paralleling an optical axis of the lens module, or drivers providing movement power with the moving direction thereof paralleling the optical axis of the lens module.
An example of a driver providing rotational power with a rotational axis thereof paralleling an optical axis of the lens module is a stepping motor. Such drivers require additional transmission-transforming mechanisms to enable the lens module to move along an axis parallel to the optical axis. When the lens module arrives at a final position, no electricity is required to maintain the lens module therein. However, such drivers have many components. Thus, the structure of such drivers is complicated, and the size thereof cannot easily be reduced.
An example of a driver providing movement power with the moving direction thereof paralleling the optical axis of the lens module is a voice coil motor. Such drivers directly adjust the position of the lens module. Compared with rotational power drivers, such drivers have fewer components and are smaller. However, when the lens module arrives at a final position, electricity must be continuously supplied thereto and simultaneous control maintained in order to keep the lens module at the final position. Accordingly, automatic displacement driving devices employing such drivers consume a great deal of electrical power. The portability of cameras or optical devices employing such drivers is thus adversely affected.
In U.S. Pat. No. 6,856,469, a lens driving device is disclosed in which a magnetic member is disposed at two lens retaining positions along an optical axis direction of a lens module. This allows the lens module to be retained at the lens retaining positions by magnetic attraction between the driving magnet of the lens module and the magnetic members when the lens module is positioned at one of the lens retaining positions. However, in this device, a magnetic member must be disposed at each position in which the lens module is to be retained, reducing the flexibility of the focusing movement and adding complexity to the structure.
Hence, there is a need for an optical device for fixing and releasing a lens module with reduced size and power consumption and simplified structure.